But the warning — the first of its kind issued by the Pakistan Meteorological Department for Karachi — may set the stage for more lifesaving warnings next summer as climate change drives temperatures higher.

October temperatures in densely populated Karachi normally rise no higher than 35 or 38 degrees Celsius, said Abdul Rashid, director of the Pakistan Meteorological Department office in Karachi.

Heat waves in October are "extremely rare incidents," he said.

But being unprepared for extreme heat can be deadly.

In 2015, a June heat wave killed about 1,500 people in Karachi, Pakistan's largest city, and left over 70,000 hospitalized, most with heat stroke.

Officials are now working to try to avoid a repeat of that heat disaster — a particular challenge as climate change brings ever-hotter years, particularly in already broiling South Asia.

"We now keep a closer watch on temperature, air, humidity [and] sunlight parameters of the Bay of Bengal and Arabian Sea, and register these parameters regularly in the weather charts, which helped predict the October heat wave more accurately and timely," Rashid told Reuters.

The Karachi office also has its own heat wave forecast division, with advanced computer systems connected to five heat wave monitoring stations recently installed around the city, he said.

The system was set up following World Meteorological Organization warnings that more frequent and intense heat waves were becoming a possibility in the region.

For Karachi's mayor, the alert provided time to send out text alerts, contact media, warn hospitals and water and power utility officials, and set up special units for heat victims in 13 city hospitals.

Dr. Seemi Jamali, head of emergencies at the state-run Jinnah Postgraduate Medical Center in Karachi, said the warning gave time to stock extra medicine, set aside beds and put medical staff on high alert.

"This really helped quickly arrange medical care facilities in hospitals for heat wave victims and avoid possible deaths," she said in an interview in her office.

Residents of Karachi said the unusual October heat is a worry.

"Octobers have remained always warm in the port city, but I never experienced this blistering heat wave in all my life in this month, which made our home feel like a furnace," said Saba Karim, a 43-year-old garment factory worker.

"We all five family members, including my husband, stayed indoors during the heat wave days and would go outside only during night hours to buy groceries," she recalled.

Ghulam Rasul, head of the Pakistan Meteorological Department in Pakistan, said the country may be seeing a change in its traditional pattern of onshore winds blowing cooler air into Karachi over the summer months.

The lack of that wind was one driver behind Karachi's October heat wave, he said.

"Temperatures in the Arabian Sea are showing gradual rising trends for the last six years because of strange weather patterns, which most likely increase the frequency and intensity of cyclones, heat waves, and torrential rains in months in which these were never or rarely seen before," said Rasul, who is also Pakistan's permanent representative to the World Meteorological Organization.